This invention relates to chain stitch sewing machines and, more particularly to double pointed looper mechanisms for such sewing machines.
Single thread, chain stitch sewing machines utilizing double pointed loopers are commonly used in machines for sewing buttons onto garments and sewing a series of substantially superimposed stitches for tacking together multiple pieces of material. Such machines are well known in the art. See, for example, U.S. Pat. No. 2,410,679, issued Nov. 5, 1946 to Pikul which discloses a double pointed looper mechanism actuated by a rotary cam which in turn is driven through a worm and worm gear coupling to the arm shaft. This mechanism is relatively complex and costly to manufacture. A simpler, more compact mechanism for driving a double pointed loop is disclosed in U.S. Pat. No. 3,165,080, issued Jan. 12, 1965 to Castellitti. This patent discloses an actuating mechanism for the looper comprising a looper biasing spring having one end attached to the looper and the other end attached to a shiftable base plate. As the base plate is shifted in one direction or the other by operation of the feed mechanism, the spring causes the looper to pivot slightly off center in one direction or the other in correspondence thereto. A V shaped slot formed in the looper serves as a cam track for a drive pin which is made to oscillate vertically along an arcuate path, thereby tilting the looper alternately in one direction, then the other. A disadvantage of this type of construction is that the drive pin does not positively track the V shaped slot and may become lodged on the lower point of the V shaped slot under certain conditions. This potential problem could be obviated by providing a positive blocking of alternately one side of the V shaped slot then the other so that the drive pin must track the side of the V shaped slot that is not blocked.
It is therefore an object of this invention to provide a double pointed looper actuating mechanism wherein the drive pin positively tracks the looper pivoting cam.
It is another object of this invention to provide a double pointed looper actuating mechanism of simple construction, and few parts, that is relatively inexpensive to manufacture and maintain.
Other objects and advantages of the invention will become apparent through reference to the accompanying drawings and descriptive matter which illustrates a preferred embodiment of this invention.